What is the minimum square foot per student requirement for individual
classrooms for schools in the state of Illinois, Chicago metropolitan
area e.g. DuPage County, Kane county.  This question pertains to
classroom footage for special education, self contained building.

This a free comment, not an "answer" to your question.

I can understand your concern after browsing some sites on the subject.

The first site gives a very old recommendation (!) for  20 sq.ft. per
student in a room with moveable facilities.
http://www.olafire.com/Coroner.asp

http://www.ncbg.org/schools/organizing_guide.htm
   Scroll down to ?overcrowding?.

This site may also be of help:
http://www.nfpa.org/itemDetail.asp?categoryID=720&itemID=20214&URL=Publications/NFPA%20Journal%AE/September%20/%20October%202003/Columns

The subject relates primarily to the Chicago Fire Prevention Code, but
it does not seem to be available online.

But maybe my amateur attempt will elicit some better help.